1. David Franklin, P.E. ESSB Winter 2017
DC Arc Flash
David Franklin, P.E.
ESSB Winter 2017

2. How did we get here?
Increased use of DC (PV, Wind Turbines and other Stored Energy means)
IEEE 1584 only focuses on AC
NFPA 70E-2015 only standard that discusses DC
Existing calculation methods too conservative
Requires excessive PPE
Increased approach boundaries

3. What’s wrong with being conservative?
Difficult to perform online maintenance
Cost impacts
Space limitations

4. NFPA 70E-2015 Basis Reference NFPA 70E-2015 Annex D.5.
Perform DC Arc Flash Risk and Hazard Assessment
Arc Flash Incident Energy based on Maximum Power Method
Maximum power delivered at when Varc = 0.5 x Vsource
Arcing Current - Iarc = ½ Ibf,
DC Incident Energy - IEin = 0.01 x Vsource x Iarc x Tarc / D2
Tables provided in 70E commensurate with arc flash energies.

5. Other Calculation Methods
Linear Solution, Ohm’s Law – Iarc = Vsource / (Rarc + Rbatt + Rcable)
Have to determine Rarc though
ETAP DC AF Module
Circuit iteration through assuming Iarc (typically start at ½ If)
Stokes and Oppenlander – Rarc = (20 x x zg) / Iarc0.88